Tailstoce



Sept. 1, 1931. E. J. svENsoN 1,821,331

` TAILTocK Filed March 19, 1928 Lneszvemsorz 7M @$55 Patented Sept. 1,1931 UNITED STATES PATENT 4OFFICE ERNEST SVENSON, F ROCKFOR-D, ILLINOIS,ASSIGNOR T0 ASUND'STRAND MACHINE TOOL C0., OF ROCKFORD, ILLINOIS,1 A.CORPORATION OF ILLINOIS TAILSTOCB Application led March 19, 1928.SerialA No. 262,672.

i for such work it is the practice to employ high rates of cutter feedand relatively heavy cuts, which conditions have heretofore resulted inthe production of a high percentage of defective work: The large radialthrust of the cutter has a tendency to move the work [radiallyrelatively to the tailstock center which results-in an eccentricity ofthe work if there is any play whatsoever between the work piece andcenter. In order to overcome this source of defective work, it isnecessary cessive wear of the to 'apply' sufficient end thrust to thetailstock center to overcome the tendency of the work to run out underthe impulse of the radial thrust. Y

Such an application of force axially of the tailstock however, has beenfound to result in a diiiiculty which is even more serious than the onewhich it is intended to overcome, namely, excessive wear upon thebearings which support the tailstock center. The wearing of thesebearings results in a wobbling of the center and therefore the produc#tion lof inaccurate work.

A more specific object of the invention is to provide a tailstock of newand improved construction which will 'prevent radial and end play of thecenter and make possible the high speed production of accurately turnedwork. e

Another object is to provide a novel mounting for a tailstock centerembodying antifriction bearings arranged so as to avoid exbearings dueto thrust loads.

Other objects and advantages will become apparent from the followingdescription and from the drawing, in which the figure shows a fragmentallongitudinal centralsectional view of a tailstock embodying thepreferred form of the invention.

While the invention is herein shown embodied in a lathe tailstockconstruction hlaving actuating means of the fluid-pressure operatedtype, it is to be understood that it is not intended to limitfftheinvention to' tailstocks embodying this particular type 'of `actuatingmeans, it being contemplated that the invention might be equally as wellembodied in tailstocks having the common screw-thread type of manualoperating means. The scope of the invention will be pointed out in theappended claims.

The form of the invention chosen for purposes of disclosure is shownembodied in a lathe tailstock of the pressure-fluid' oper- I atedtypehaving a cylindrical body portion 1 cast integrally with a suitablesupporting frame 2. The body 1 has an internal bore 3 adapted to receivea movable body` or plunger 4 whichlis slidable in the borelongitudinally of the lathe.

The range of movement of the plunger 4 is such that the forward end(left end as Y shown herein) moves beyond the end of the surroundingcylindrical body 1 and when the movement of the plunger is reversedthere is a tendency to carry particles of dust or metal between thecontacting surfaces of the plunger and the boreA 3. In order to preventsuch entrance of dirt and to assist in the lubrication of thesesurfaces, a collar 5 having an internal groove 6 is secured tothe end ofthe body 1 surrounding the plunger \and suitable packing is positionedin the groove so as to contact the surface of the plunger.

Any preferred means maybe provided for reciprocatin the plunger 4. Thismeans in the present instance is of the fluid-pressure operated type andcomprises a double acting cylinder 7 mounted on the rear end of the body1 and hav-ing a piston 8 therein connected by means of a rod 9and-bushing 10 to the rear end of the plunger 4. For the purposeA ofsecuring the cylinder 7 to the end of the body 1, an end wall 11 issecured to the body by means of headed screws 12 which extend throughsuitable apertures inthe Walll and engage the walls of the body. Acentrally'y positioned threaded aperture 14 is formed in the end wall114 to receive the threaded exterior of a stuffing box 15 on the end ofthe cylinder 7 and thus firmly secure the cylinder to the end wall l1.

A tailstock center or spindle 16 is mounted in a central bore 17 whichextends longitudinally of the plunger 4 so that the oney end of thecenter projects forwardly from the plunger to engage a work piece whenthe plunger is moved forwardly by the piston 9. In order to avoidwearing of the center hole in the work piece, the center 16 is rotatablymounted in the plunger 4 so as to rotate with the workpiece and ispreferably mounted on ball bearings arranged so as to elminate radialand end play of the center in the plunger and thereby prevent wobblingof the center 16.`

For thepurpose of takingy the radial load impressed upon the center 16,two single row ball bearings 18, 19 are positioned adjacent the forwardend of the center 16 and a double row ball bearing 2() is positioned atthe rear end thereof. Since the two single row ball bearings 18, 19 arepositioned so close to the work engaging portion of the spindle 16, itI

is essential that radial play in the bearings be practically eliminated.Factors which might cause Wear on the bearings and thus cause suchradial play must also be eliminated in order to insure satisfactoryoperation of the tailstock over a reasonably long period of time.

To this end the outer races 23 and 24 of the bearings 18, 19 are mountedwithin the b-ore 17 so as to permit slight axial movement thereof, thusto avoid axial or thrust load thereon. In order that the outer races 23,

24 may be so moved by the spindle without changing the direction ofapplication of force to the balls 18, 19, the two single row bearingsare arranged to cooperate with each othel` and act as a unit, all springand play between the balls and races of these bearings being removed.This is accomplished preferably by grinding of the adjacent faces 25, 26of the inner races 21, 22 so that when these races are clamped tightlytogether as hereinafter described, the balls are normally subjected to aconstant load slightly ,greater than the average working load on theballs. By assembling the .bearings in this manner the radial playtherein is eliminated and due to the initial pressure exerted on theparts of the bearing, any displacement which might otherwise be causedby compression of the parts is effectively avoided. Due to the angulardirection of the forces applied to the balls, the necessary axialmovement of the outer races is accomplished without changing therelative positions of the parts of either of the bearings 18 and 19.Thus one of the primary causes of wear is elimia nated and the lift ofthe bearing prolonged.

31 of the rear bearing 20. A nut 32 engages the threaded end 33 of thecenter at the other side of the rear bearing and is arranged to clampthe assembled races 21, 22 of the front bearings, the spacing sleeve 30and the race 31 of the rear bearing together on the spindle. This placesthe desired load upon the front bearings 18, 19 and properly positionsthe assembled parts.

In order to exclude dust or other foreign matter which might beinjurious tothe bearings contained within the plunger' 4, a protectivecollar 35 is attached to the forward end of'the plunger and surroundingthe flange 28 on the center. This collar is preferably provided with aninternal groove 36 in which suitable packing 37 may be positioned.

For the purpose of taking the thrust load impressed upon the spindle 16,a ball bearing 40 is provided. This bearing comprises two similar races4l and 42 herein illustrated as surrounding the sleeve y30 rearwardly ofthe flange 29. The forward race 41 abuts the flange 29 and may be fixedupon the sleeve 30 by a light press fit. Both of the races are arrangedfor a slight clearance between their outer edges and the walls of thebore, and the rear race 42 has a small clearance between its inner edgeand the outer surface of the sleeve 30. The rear race 42 is arranged toabut a thrust washer 43 which is positioned against a shoulder 44 formedWithin the bore of the plunger. This washer is preferably arranged so asto have a substantial clearance between its outer edge and the wall ofthe bore and between its inner edge and the sleeve and floattherebetween and is fixed against rotation relatively to the plunger bya pin 45 secured to the race and radially slidable in the wall of theplunger. Thus the rear race may float between the plunger and sleeve andthe bearing is arranged so as tol avoid taking any radial load whichmighttend to wear the bearing.

In order to prevent axial separation of the two races 41 and42 whichwould allow the balls 40 to drop out of their proper positions, means isprovided to press the races toward each other. In the `present instancethis means comprises -a` plurality of expansive coil springs 46positioned in axially extending bores 47 formed at spaced intervalsabout the thrust washer 44. The springs 46 are arranged of single rowball bearings mounted adjacent to abut the rear side of the race 42.Thus in:l

case there should be any sli ht end play of the center when removed thesprings retain the thrust bearing parts in their proper operatingrelation. A

From the foregoing it will be apparent that the invention provides atailstock which will support a rotating work piece so as to produceaccurately turned work. The novel arrangement of radial bearingsprevents radial play of the center and this. in conjunction with theeffective mounting for the thrust bearing avoids excessive wear andmakes it possible to chuck the work with great axial force.

It will also be apparent that the parts may be readily assembled and areconveniently removable for inspection and replacement. By removing theprotective collar 35 and the pin 45, the center `and all the partswit-hin the plunger may be withdrawn` axially.

I claim as my invention;

1. A lathe tailstock comprising, in com! bination, a supportin framehaving a bore, a plunger reciproca ly mounted therein, means forreciprocating said plunger, a center in the forward end of. saidplunger, and bearing means for rotatably supporting said centercomprising n. ball bearing having an inner race mounted. near the rearend of said center and having an outer race arranged for slidingmovement on said plunger, a pair each other on said center near itsforward end, means to clamp the two inner iaces thereof .togetheraxially so as to place the balls in said bearings under a constantpressure tending to maintain said outer races abutting each other, anantifriction thrust bearing comprising a forward race fixed on saidcenter, a rear race loosely surrounding said center and balls interposedbetween said i'aces, a thrust washer mounted in said plunger and adaptedto abut said rear race, and resilient means interposed between saidwasher and said rear race tending to urge said rear race towards saidforward race so as to prevent displacenient of said balls.

2. A lathe tailstock comprisingin combination, a supporting frame havinga bore, a plunger reciprocably mounted therein, means for reciprocatingsaid plunger, a

centering spindle Vin the forward end of said plunger, and bearing meansfor rotatably supporting said spindle comprising a ball bearing mountedon the spindle near the rear end thereof and arranged for axial iioatinglmovement relatively to said plunger, a pair of single row ball bearingsmounted adjacent each other near the forward end of the spindle andhaving outer races arranged for axial sliding movement on said plunger,means for clamping the inner races of said bearings together axially soas to place the balls in said bearings under constant pressure, and a.ball lthrust bearing arranged to float radially relatively tosaidplunger. rom the work,

3. lathe tailstock comprising, in combination, a body, a plunger mountedfor longitudinal sliding movement relatively to said body, said plungerhaving a longitudinal bore formed therein, a spindle rotatably mountedin said bore and having a shoulder near its forward end, a ball bearingpositioned on said spindle having an inner race rearwardly of andabutting said shoulder, a

sleeve surrounding said spindley and abutting the rear side of saidinner race, a second ball bearing on the rear end of said spindle havingan inner race abutting the end of said sleeve, and a nut threaded on therear end of said spindle and abutting the rear end of said inner racewhereby said front and rear bearings may be clamped in position.`

4. In a lathe tailstock, the combination of a spindle having a shoulder`near its forward end, a ball bearing on said spindle rearwardly of\saidshoulder and having .an inner race abutting said shoulder, a. sleevesurrounding said spindle and abutting the rear side of said inner race asecond bearing on the rear-end of said spindle having an inner raceabutting the rear end of said sleeve, and a nut threaded on the rear endof said spindle engaging the ings in position on said spindle.

5. A tailstock comprising in combination,

a frame, a longitudinally slidable plunger mounted therein, a workcenter rotatably mounted in said plunger, radial bearings interposedbetween said center and said plunger so as to permit slight longitudinalmovement of the center relative to the plunger, and a ball thrustbearing interposed between said center and said plunger, said bearingcomprising a front race fixed on said center,

an abutment on the plunger against which the vrear race. may bear whenpressure is applied to the spindle to positively determine the axialposition of the spindle, and resilient means lpressing forwardly on saidrear race to hold said bearing parts in assembled relation when thespindle is not in engagement `with a =work piece.

6. In a lathe tailstock, a body, a spindle rotatably mounted therein,bearing means for the forward end of said spindle comprising two singlerow ball bearings having inner races arranged soas to be separated in anaxial direction when the outer races abut each other, and meansassociated with said spindle operable to clamp said inner races togetheraxially so as to exert a normal wo-rking pressure on the balls of thebearing.

7. A tailstock comprising, in combination, a body, a plungerlongitudinally slidable in said body, said plunger having a longitudinalbore formed therein, a spindle rotatably mounted in said bore and havinga shoulder near its adjacent to its forward end, a first antifrietionradial bearing having an outer race engaging said bore for floatingmovement longitudinally thereof and an inner race surrounding saidspindle and abutting said Shoulder, a sleeve surrounding said spindleand having one end abutting the rear side 0f said inner race, anantifriction thrust bearing having one race engaging said sleeve andanother race operatively engaging a shoulder in said bore for floatingmovement radially of said bore, a second antifriction radial bearinghaving an outer race' engaging said bore for floating movementvlongitudinally of the bore and an inner race surrounding the spindleand engaging the other end of said sleeve, and a nut threaded on therear end of said spindle and engaging the inner race of i said secondradial bearing for clamping the inner races of said radial bearings inposition on the spindle.

8. In a lathe tailstock, the combination with a body having a spindlerotatably mounted therein,of a ball thrust bearing having one raceabutting a shoulder formed on Said spindle, a radially floating mountinginterposed between said bodv and the other race of said bearing, andmeans acting between said body and said other race arranged to take upaxial play in said bearing.

9. A lathe tailstock comprising, in combination, a body, a centeringspindle rotatably mounted therein, a radial bearing for the forward endof said spindle floating axially of said body, a thrust bearing for saidspindle floating radially of said body, adjustable means for taking upradial play in said radial bearing, and means automatically operable totake up axial play in said thrust bearing.

10. A tailstock comprising, in combination, a body, a plunger mountedfor longis tudinal sliding movement relative to said body, -said plungerhaving a longitudinal bore formed therein, a spindle rotatably mountedin said bore and having a shoulder ing radial load positioned on saidspindle and having an inner race rearwardly of and abutting saidshoulder, a sleeve surrounding said spindle and abuttinnr the rear sideof said inner race, a ball thru-st bearing carried by said sleeve, asecond ball bearing for taking radial load positioned on the rear end ofsaid spindle and having an inner race abutting the rear end of saidsleeve, and a nut threaded on the rear-end of said spindle and engagingsaid inner race wherebv the'three bearings may be clamped in position onthe spindle.

11. A lathe tailstock comprising a body, a longitudinallv adjustableplunger in said i body, a spindle rotatably mounted in said plunger,bearing means for the forward end of said spindle comprising twobearings each having an inner and an outer race and a single row ofantifriction members, the two -outer races engaging each other and theinner races being spaced from each other longitudinally of said spindle,said members and said races being formed so that relative movement osaid inner races axially of the spindle toward each other acts to takeup radial play in said bearings, and means associated with said spindleoperable to clamp -said inner races together axially of the spindle toexert a normal Working pressure on said antifriction members.

In .testimony whereof, I have hereunto affixed my signature. A

ERNEST J SVENSON.

forward end, a ball bearing for tak-

